Editing Computer programming

{{Short description|Process to create executable computer programs}}
{{Use mdy dates|date=November 2020}}
{{Use American English|date=November 2020}}
{{Software development process}}
'''Computer programming''' or '''coding''' is the composition of sequences of instructions, called [[computer program|programs]], that [[computer]]s can follow to perform tasks.<ref>{{cite web|url=http://yearofcodes.tumblr.com/what-is-coding|title=What is coding|last=Bebbington|first=Shaun|year=2014|website=Tumblr|url-status=live|archive-url=https://web.archive.org/web/20200429195646/https://yearofcodes.tumblr.com/what-is-coding|archive-date=2020-04-29|access-date=2014-03-03}}</ref><ref>{{cite web|url=http://yearofcodes.tumblr.com/what-is-programming|title=What is programming|last=Bebbington|first=Shaun|year=2014|website=Tumblr|url-status=live|archive-url=https://web.archive.org/web/20200429195958/https://yearofcodes.tumblr.com/what-is-programming|archive-date=2020-04-29|access-date=2014-03-03}}</ref> It involves designing and implementing [[algorithm]]s, step-by-step specifications of procedures, by writing [[source code|code]] in one or more [[programming language]]s. Programmers typically use [[high-level programming language]]s that are more easily intelligible to humans than [[machine code]], which is directly executed by the [[central processing unit]]. Proficient programming usually requires expertise in several different subjects, including knowledge of the [[Domain (software engineering)|application domain]], details of programming languages and generic code [[library (computing)|libraries]], specialized algorithms, and [[Logic#Formal logic|formal logic]].

Auxiliary tasks accompanying and related to programming include [[Requirements analysis|analyzing requirements]], [[Software testing|testing]], [[debugging]] (investigating and fixing problems), implementation of [[Build automation|build systems]], and management of derived [[Artifact (software development)|artifacts]], such as programs' [[machine code]]. While these are sometimes considered programming, often the term ''[[software development]]'' is used for this larger overall process – with the terms ''programming'', ''implementation'', and ''coding'' reserved for the writing and editing of code per se. Sometimes software development is known as ''[[software engineering]]'', especially when it employs [[formal methods]] or follows an [[engineering design process]].

==History==
[[File:Ada lovelace.jpg|thumb|[[Ada Lovelace]], whose notes were added to the end of [[Luigi Menabrea]]'s paper included the first [[algorithm]] designed for processing by [[Charles Babbage]]'s [[Analytical Engine]]. She is often recognized as history's first computer programmer.]]
{{See also|Computer program#History|Programmer#History|History of programming languages}}

[[Program (machine)|Programmable devices]] have existed for centuries. As early as the 9th century, a programmable [[music sequencer]] was invented by the Persian [[Banu Musa]] brothers, who described an automated mechanical [[flute]] player in the ''[[Book of Ingenious Devices]]''.<ref name=Koetsier>{{cite journal |last1=Koetsier |first1=Teun  |year=2001 |title=On the prehistory of programmable machines: musical automata, looms, calculators |journal=Mechanism and Machine Theory |volume=36 |issue=5 |pages=589–603 |publisher=Elsevier |doi=10.1016/S0094-114X(01)00005-2 }}</ref><ref>{{cite journal |last1=Kapur |first1=Ajay |last2=Carnegie |first2=Dale |last3=Murphy |first3=Jim |last4=Long |first4=Jason |title=Loudspeakers Optional: A history of non-loudspeaker-based electroacoustic music |journal=[[Organised Sound]] |date=2017 |volume=22 |issue=2 |pages=195–205 |doi=10.1017/S1355771817000103 |publisher=[[Cambridge University Press]] |issn=1355-7718|doi-access=free }}</ref> In 1206, the Arab engineer [[Al-Jazari]] invented a programmable [[drum machine]] where a musical mechanical [[automaton]] could be made to play different rhythms and drum patterns, via pegs and [[Cam (mechanism)|cam]]s.<ref>{{Cite journal|title=The Museum of Music: A History of Mechanical Instruments|first=Charles B.|last=Fowler|journal=Music Educators Journal|volume=54|issue=2|date=October 1967|pages=45–49|doi=10.2307/3391092|jstor=3391092|s2cid=190524140}}</ref><ref name=Sharkey>[[Noel Sharkey]] (2007), [https://web.archive.org/web/20070629182810/http://www.shef.ac.uk/marcoms/eview/articles58/robot.html A 13th Century Programmable Robot], [[University of Sheffield]]</ref> In 1801, the [[Jacquard loom]] could produce entirely different weaves by changing the "program" – a series of [[Card stock|pasteboard]] cards with holes punched in them.

[[Code-breaking]] algorithms have also existed for centuries. In the 9th century, the [[Mathematics in medieval Islam|Arab mathematician]] [[Al-Kindi]] described a [[cryptographic]] algorithm for deciphering encrypted code, in ''A Manuscript on Deciphering Cryptographic Messages''. He gave the first description of [[cryptanalysis]] by [[frequency analysis]], the earliest code-breaking algorithm.<ref>{{cite book |last1=Dooley |first1=John F. |title=A Brief History of Cryptology and Cryptographic Algorithms |date=2013 |publisher=Springer Science & Business Media |isbn=9783319016283 |pages=12–3}}</ref>

The first [[computer program]] is generally dated to 1843 when mathematician [[Ada Lovelace]] published an [[algorithm]] to calculate a sequence of [[Bernoulli numbers]], intended to be carried out by [[Charles Babbage]]'s [[Analytical Engine]].<ref name="IEEE">{{Cite journal | last1 = Fuegi | first1 = J. | last2 = Francis | first2 = J. | title = Lovelace & Babbage and the Creation of the 1843 'notes' | journal = IEEE Annals of the History of Computing | volume = 25 | issue = 4 | pages = 16 | year = 2003 | doi = 10.1109/MAHC.2003.1253887}}</ref> The algorithm, which was conveyed through notes on a translation of Luigi Federico Menabrea's paper on the analytical engine was mainly conceived by Lovelace as can be discerned through her correspondence with Babbage. However, Charles Babbage himself had written a program for the AE in 1837.<ref name="IEEE2021">{{Cite journal | last1 = Rojas | first1 = R. | title = The Computer Programs of Charles Babbage | journal = IEEE Annals of the History of Computing | volume = 43 | issue = 1 | pages = 6–18 | year = 2021 | doi = 10.1109/MAHC.2020.3045717}}</ref><ref name="IEEE2024">{{Cite journal | last1 = Rojas | first1 = R. | title = The First Computer Program | journal = Communications of the ACM | volume = 67 | issue = 6 | pages = 78–81 | year = 2024 | doi = 10.1145/3624731| doi-access = free | url = https://refubium.fu-berlin.de/bitstream/fub188/44090/1/3624731.pdf }}</ref> Lovelace was also the first to see a broader application for the analytical engine beyond mathematical calculations. 

[[File:PunchCardDecks.agr.jpg|thumb|Data and instructions were once stored on external [[punched card]]s, which were kept in order and arranged in program decks.]]
In the 1880s, [[Herman Hollerith]] invented the concept of storing ''data'' in machine-readable form.<ref>{{cite web|url=http://www.columbia.edu/acis/history/hollerith.html|title=Columbia University Computing History – Herman Hollerith|last=da Cruz|first=Frank|date=2020-03-10|website=Columbia University|publisher=Columbia.edu|url-status=live|archive-url=https://web.archive.org/web/20200429210742/http://www.columbia.edu/cu/computinghistory/hollerith.html|archive-date=2020-04-29|access-date=2010-04-25}}</ref> Later a [[plugboard|control panel]] (plug board) added to his 1906 Type I Tabulator allowed it to be programmed for different jobs, and by the late 1940s, [[unit record equipment]] such as the [[IBM 602]] and [[IBM 604]], were programmed by control panels in a similar way, as were the first [[electronic computer]]s. However, with the concept of the [[stored-program computer]] introduced in 1949, both programs and data were stored and manipulated in the same way in [[computer memory]].<ref>{{cite web |title=Memory & Storage {{!}} Timeline of Computer History {{!}} Computer History Museum |url=https://www.computerhistory.org/timeline/memory-storage/ |website=www.computerhistory.org |access-date=3 June 2021 |archive-date=May 27, 2021 |archive-url=https://web.archive.org/web/20210527071533/https://www.computerhistory.org/timeline/memory-storage/ |url-status=live }}</ref>

===Machine language===
[[Machine code]] was the language of early programs, written in the [[instruction set architecture|instruction set]] of the particular machine, often in [[binary numeral system|binary]] notation. [[Assembly language]]s were soon developed that let the programmer specify instructions in a text format (e.g., ADD X, TOTAL), with abbreviations for each operation code and meaningful names for specifying addresses. However, because an assembly language is little more than a different notation for a machine language,  two machines with [[Comparison of instruction set architectures|different instruction sets]] also have different assembly languages.

[[File:IBM402plugboard.Shrigley.wireside.jpg|thumb|Wired [[plugboard|control panel]] for an [[IBM 402 Accounting Machine]]. Wires connect pulse streams from the card reader to counters and other internal logic and ultimately to the printer.]]

===Compiler languages===
{{See also|Compiler}}
[[High-level language]]s made the process of developing a program simpler and more understandable, and less bound to the underlying [[Computer hardware|hardware]]. 
The first compiler related tool, the [[A-0 System]], was developed in 1952<ref>{{cite book |last1=Ridgway|first1=Richard|title=Proceedings of the 1952 ACM national meeting (Toronto) on - ACM '52 |chapter=Compiling routines |date=1952|pages=1–5|doi=10.1145/800259.808980|isbn=9781450379250|s2cid=14878552|doi-access=free}}</ref> by [[Grace Hopper]], who also coined the term 'compiler'.<ref name="wikles1968">[[Maurice V. Wilkes]]. 1968. Computers Then and Now. Journal of the Association for Computing Machinery, 15(1):1–7, January. p. 3 (a comment in brackets added by editor), "(I do not think that the term compiler was then [1953] in general use, although it had in fact been introduced by Grace Hopper.)"</ref><ref name="computerhistory.org">[http://www.computerhistory.org/events/lectures/cobol_06121997/index.shtml] The World's First COBOL Compilers   {{webarchive|url=https://web.archive.org/web/20111013021915/http://www.computerhistory.org/events/lectures/cobol_06121997/index.shtml|date=13 October 2011}}</ref> [[FORTRAN]], the first widely used high-level language to have a functional implementation, came out in 1957,<ref name = bergstein>{{cite web|url=https://www.nbcnews.com/id/wbna17704662|title=Fortran creator John Backus dies |last=Bergstein|first=Brian|date=2007-03-20|website=NBC News|url-status= live|archive-url=https://web.archive.org/web/20200429211030/http://www.nbcnews.com/id/17704662|archive-date=2020-04-29 |access-date=2010-04-25}}</ref> and many other languages were soon developed—in particular, [[COBOL]] aimed at commercial data processing, and [[Lisp (programming language)|Lisp]] for computer research.

These compiled languages allow the programmer to write programs in terms that are syntactically richer, and more capable of [[abstraction (computer science)|abstracting]] the code, making it easy to target varying machine instruction sets via compilation declarations and [[Heuristic (computer science)|heuristics]]. Compilers harnessed the power of computers to make programming easier<ref name = bergstein/> by allowing programmers to specify calculations by entering a formula using [[infix notation]].

===Source code entry===
{{See also|Computer programming in the punched card era}}
Programs were mostly entered using punched cards or [[paper tape]]. By the late 1960s, [[data storage device]]s and [[computer terminal]]s became inexpensive enough that programs could be created by typing directly into the computers. [[Text editor]]s were also developed that allowed changes and corrections to be made much more easily than with [[Punched card sorter|punched cards]].

==Modern programming==

===Quality requirements===
{{main|Software quality}}
Whatever the approach to development may be, the final program must satisfy some fundamental properties. The following properties are among the most important:<ref>{{cite magazine |magazine=[[InformationWeek]]
   |url=https://www.informationweek.com/cloud/nist-to-develop-cloud-roadmap/d/d-id/1093958?
   |title=NIST To Develop Cloud Roadmap |date=November 5, 2010
   |quote=Computing initiative seeks to remove barriers to cloud adoption in security, interoperability, portability and reliability.}}</ref>
<ref>{{cite news |newspaper=[[Computerworld]]|date=April 9, 1984  |page=13
|title=What is it based on
|quote=Is it based on ... Reliability Portability. Compatibility}}</ref>
*[[Reliability engineering#Software reliability|Reliability]]: how often the results of a program are correct. This depends on conceptual correctness of algorithms and minimization of programming mistakes, such as mistakes in resource management (e.g., [[buffer overflow]]s and [[race condition]]s) and logic errors (such as division by zero or [[off-by-one error]]s).
*[[Robustness (computer science)|Robustness]]: how well a program anticipates problems due to errors (not bugs). This includes situations such as incorrect, inappropriate or corrupt data, unavailability of needed resources such as memory, operating system services, and network connections, user error, and unexpected power outages.
*[[Usability]]: the [[ergonomics]] of a program: the ease with which a person can use the program for its intended purpose or in some cases even unanticipated purposes. Such issues can make or break its success even regardless of other issues. This involves a wide range of textual, graphical, and sometimes hardware elements that improve the clarity, intuitiveness, cohesiveness, and completeness of a program's user interface.
*[[Software portability|Portability]]: the range of [[computer hardware]] and [[operating system]] platforms on which the source code of a program can be [[compiled]]/[[interpreter (computing)|interpreted]] and run. This depends on differences in the programming facilities provided by the different platforms, including hardware and operating system resources, expected behavior of the hardware and operating system, and availability of platform-specific compilers (and sometimes libraries) for the language of the source code.
*[[Maintainability]]: the ease with which a program can be modified by its present or future developers in order to make improvements or to customize, fix [[Software bug|bugs]] and [[Vulnerability (computing)|security holes]], or adapt it to new environments. Good practices<ref>{{Cite web |url=http://wisdomgeek.com/programming/tips-become-good-programmer |title=Programming 101: Tips to become a good programmer - Wisdom Geek |date=May 19, 2016 |website=Wisdom Geek |language=en-US |access-date=2016-05-23 |archive-date=May 23, 2016 |archive-url=https://web.archive.org/web/20160523063915/http://wisdomgeek.com/programming/tips-become-good-programmer |url-status=live }}</ref> during initial development make the difference in this regard. This quality may not be directly apparent to the end user but it can significantly affect the fate of a program over the long term.
*[[Algorithmic efficiency|Efficiency]]/[[performance engineering|performance]]: Measure of system resources a program consumes (processor time, memory space, slow devices such as disks, network bandwidth and to some extent even user interaction): the less, the better. This also includes careful management of resources, for example cleaning up [[temporary file]]s and eliminating [[memory leak]]s. This is often discussed under the shadow of a chosen programming language. Although the language certainly affects performance, even slower languages, such as [[Python (programming language)|Python]], can execute programs instantly from a human perspective. Speed, resource usage, and performance are important for programs that [[Bottleneck (software)|bottleneck]] the system, but efficient use of programmer time is also important and is related to cost: more hardware may be cheaper.
Using [[Test automation|automated tests]] and [[Fitness function|fitness functions]] can help to maintain some of the aforementioned attributes.<ref>{{Cite book |title=Fundamentals of Software Architecture: An Engineering Approach |publisher=O'Reilly Media |year=2020 |isbn=978-1492043454}}</ref>

===Readability of source code===
In computer programming, [[readability]] refers to the ease with which a human reader can comprehend the purpose, [[control flow]], and operation of [[source code]]. It affects the aspects of quality above, including portability, usability and most importantly maintainability.

Readability is important because programmers spend the majority of their time reading, trying to understand, reusing, and modifying existing source code, rather than writing new source code. Unreadable code often leads to bugs, inefficiencies, and [[Code duplication|duplicated code]]. A study found that a few simple readability transformations made code shorter and drastically reduced the time to understand it.<ref>{{cite journal|doi=10.1145/358589.358596|title=Improving computer program readability to aid modification|journal=Communications of the ACM|volume=25|issue=8|pages=512–521|year=1982|last1=Elshoff|first1=James L.|last2=Marcotty|first2=Michael|s2cid=30026641|doi-access=free}}</ref>

Following a consistent [[programming style]] often helps readability. However, readability is more than just programming style. Many factors, having little or nothing to do with the ability of the computer to efficiently compile and execute the code, contribute to readability.<ref>{{cite web|url=http://docforge.com/wiki/Readability|title=Readability|author=Multiple (wiki)|work=Docforge|url-status=live|archive-url=https://web.archive.org/web/20200429211203/http://www.docforge.com/wiki/Readability|archive-date=2020-04-29|access-date=2010-01-30}}</ref> Some of these factors include:
*Different [[indent style]]s (whitespace)
*[[Comment (computer programming)|Comments]]
*[[decomposition (computer science)|Decomposition]]
*[[Naming conventions (programming)|Naming conventions]] for objects (such as variables, classes, functions, procedures, etc.)

The [[separation of presentation and content|presentation]] aspects of this (such as indents, line breaks, color highlighting, and so on) are often handled by the [[source code editor]], but the content aspects reflect the programmer's talent and skills.

Various [[visual programming language]]s have also been developed with the intent to resolve readability concerns by adopting non-traditional approaches to code structure and display. [[Integrated development environment]]s (IDEs) aim to integrate all such help. Techniques like [[Code refactoring]] can enhance readability.

===Algorithmic complexity===
The academic field and the engineering practice of computer programming are concerned with discovering and implementing the most efficient algorithms for a given class of problems. For this purpose, algorithms are classified into ''orders'' using [[Big O notation]], which expresses resource use—such as execution time or memory consumption—in terms of the size of an input. Expert programmers are familiar with a variety of well-established algorithms and their respective complexities and use this knowledge to choose algorithms that are best suited to the circumstances.

===Methodologies===
The first step in most formal software development processes is [[requirements analysis]], followed by testing to determine value modeling, implementation, and failure elimination (debugging). There exist a lot of different approaches for each of those tasks. One approach popular for requirements analysis is [[Use Case]] analysis. Many programmers use forms of [[Agile software development]] where the various stages of formal software development are more integrated together into short cycles that take a few weeks rather than years. There are many approaches to the Software development process.

Popular modeling techniques include Object-Oriented Analysis and Design ([[OOAD]]) and Model-Driven Architecture ([[Model-Driven Architecture|MDA]]). The Unified Modeling Language ([[Unified Modeling Language|UML]]) is a notation used for both the OOAD and MDA.

A similar technique used for database design is Entity-Relationship Modeling ([[Entity-Relationship Model|ER Modeling]]).

Implementation techniques include imperative languages ([[Object-oriented programming|object-oriented]] or [[procedural programming|procedural]]), [[functional programming|functional languages]], and [[logic programming]] languages.

===Measuring language usage===
It is very difficult to determine what are the most popular modern programming languages. Methods of measuring programming language popularity include: counting the number of job advertisements that mention the language,<ref>{{cite web|url = http://www.computerweekly.com/Articles/2007/09/11/226631/sslcomputer-weekly-it-salary-survey-finance-boom-drives-it-job.htm|title = SSL/Computer Weekly IT salary survey: finance boom drives IT job growth|date = 11 September 2007|first = Nicholas|last = Enticknap|url-access = registration|access-date = June 24, 2009|archive-date = October 26, 2011|archive-url = https://web.archive.org/web/20111026035734/http://www.computerweekly.com/Articles/2007/09/11/226631/SSLComputer-Weekly-IT-salary-survey-finance-boom-drives-IT-job.htm|url-status = live}}</ref> the number of books sold and courses teaching the language (this overestimates the importance of newer languages), and estimates of the number of existing lines of code written in the language (this underestimates the number of users of business languages such as COBOL).

Some languages are very popular for particular kinds of applications, while some languages are regularly used to write many different kinds of applications. For example, [[COBOL]] is still strong in corporate data centers<ref>{{cite web|last1=Mitchell|first1=Robert|title=The Cobol Brain Drain|url=http://www.computerworld.com/article/2504568/data-center/the-cobol-brain-drain.html|publisher=Computer World|access-date=9 May 2015|date=2012-05-21|archive-date=February 12, 2019|archive-url=https://web.archive.org/web/20190212185631/https://www.computerworld.com/article/2504568/data-center/the-cobol-brain-drain.html|url-status=live}}</ref> often on large [[mainframe computer]]s, [[Fortran]] in engineering applications, [[scripting language]]s in [[World Wide Web|Web]] development, and [[C (programming language)|C]] in [[embedded software]]. Many applications use a mix of several languages in their construction and use.  New languages are generally designed around the syntax of a prior language with new functionality added, (for example [[C++]] adds object-orientation to C, and [[Java (programming language)|Java]] adds memory management and [[bytecode]] to C++, but as a result, loses efficiency and the ability for low-level manipulation).

===Debugging===
{{main|Debugging}}
[[File:First Computer Bug, 1945.jpg|thumb|The first known actual bug causing a problem in a computer was a moth, trapped inside a Harvard mainframe, recorded in a log book entry dated September 9, 1947.<ref>{{cite web| url = https://www.nationalgeographic.org/thisday/sep9/worlds-first-computer-bug| title = Photograph courtesy Naval Surface Warfare Center, Dahlgren, Virginia, from National Geographic Sept. 1947| date = July 15, 2020| access-date = November 10, 2020| archive-date = November 13, 2020| archive-url = https://web.archive.org/web/20201113163443/https://www.nationalgeographic.org/thisday/sep9/worlds-first-computer-bug/| url-status = live}}</ref> "Bug" was already a common term for a software defect when this insect was found.]]
Debugging is a very important task in the software development process since having defects in a program can have significant consequences for its users. Some languages are more prone to some kinds of faults because their specification does not require compilers to perform as much checking as other languages. Use of a [[static code analysis]] tool can help detect some possible problems. Normally the first step in debugging is to attempt to reproduce the problem. This can be a non-trivial task, for example as with parallel processes or some unusual software bugs. Also, specific user environment and usage history can make it difficult to reproduce the problem.

After the bug is reproduced, the input of the program may need to be simplified to make it easier to debug. For example, when a bug in a compiler can make it crash when [[parsing]] some large source file, a simplification of the test case that results in only few lines from the original source file can be sufficient to reproduce the same crash. Trial-and-error/divide-and-conquer is needed: the programmer will try to remove some parts of the original test case and check if the problem still exists. When debugging the problem in a GUI, the programmer can try to skip some user interaction from the original problem description and check if the remaining actions are sufficient for bugs to appear. Scripting and [[breakpoint]]ing are also part of this process.

Debugging is often done with [[Integrated development environment|IDE]]s. Standalone debuggers like [[GDB]] are also used, and these often provide less of a visual environment, usually using a [[command line]]. Some text editors such as [[Emacs]] allow GDB to be invoked through them, to provide a visual environment.

==Programming languages{{anchor|Languages}}==
{{Main|Programming language|List of programming languages}}
{{See also|Computer program#Languages}}

Different programming languages support different styles of programming (called ''[[programming paradigm]]s''). The choice of language used is subject to many considerations, such as company policy, suitability to task, availability of third-party packages, or individual preference. Ideally, the programming language best suited for the task at hand will be selected. Trade-offs from this ideal involve finding enough programmers who know the language to build a team, the availability of compilers for that language, and the efficiency with which programs written in a given language execute. Languages form an approximate spectrum from "low-level" to "high-level"; "low-level" languages are typically more machine-oriented and faster to execute, whereas "high-level" languages are more abstract and easier to use but execute less quickly. It is usually easier to code in "high-level" languages than in "low-level" ones.
Programming languages are essential for software development. They are the building blocks for all software, from the simplest applications to the most sophisticated ones.

[[Allen Downey]], in his book ''How To Think Like A Computer Scientist'', writes:

:The details look different in different languages, but a few basic instructions appear in just about every language:
:*Input: Gather data from the keyboard, a file, or some other device.
:*Output: Display data on the screen or send data to a file or other device.
:*Arithmetic: Perform basic arithmetical operations like addition and multiplication.
:*Conditional Execution: Check for certain conditions and execute the appropriate sequence of statements.
:*Repetition: Perform some action repeatedly, usually with some variation.

Many computer languages provide a mechanism to call functions provided by [[shared library|shared libraries]]. Provided the functions in a library follow the appropriate run-time conventions (e.g., method of passing [[argument (computer science)|arguments]]), then these functions may be written in any other language.

==Learning to program==
Learning to program has a long history related to professional standards and practices, academic initiatives and curriculum, and commercial books and materials for students, self-taught learners, hobbyists, and others who desire to create or customize software for personal use. Since the 1960s, learning to program has taken on the characteristics of a ''popular movement'', with the rise of academic disciplines, inspirational leaders, collective identities, and strategies to grow the movement and make institutionalize change.<ref>{{cite book |last1=Halvorson |first1=Michael J. |title=Code Nation: Personal Computing and the Learn to Program Movement in America |date=2020 |publisher=ACM Books |location=New York, NY |pages=3–6}}</ref> Through these social ideals and educational agendas, learning to code has become important not just for scientists and engineers, but for millions of citizens who have come to believe that creating software is beneficial to society and its members.

===Context===
In 1957, there were approximately 15,000 computer programmers employed in the U.S., a figure that accounts for 80% of the world's active developers. In 2014, there were approximately 18.5 million professional programmers in the world, of which 11 million can be considered professional and 7.5 million student or hobbyists.<ref>{{cite book |title=2014 Worldwide Software Developer and ICT-Skilled Worker Estimates |date=2014 |publisher=International Data Corporation |location=Framingham, MA}}</ref> Before the rise of the commercial Internet in the mid-1990s, most programmers learned about software construction through books, magazines, user groups, and informal instruction methods, with academic coursework and corporate training playing important roles for professional workers.<ref>{{cite book |last1=Ensmenger |first1=Nathan |title=The Computer Boys Take Over: Computers, Programmers, and the Politics and Technical Expertise |date=2010 |publisher=The MIT Press |location=Cambridge, MA}}</ref>

The first book containing specific instructions about how to program a computer may have been [[Maurice Wilkes]], [[David Wheeler (computer scientist)|David Wheeler]], and [[Stanley Gill|Stanley Gill's]] ''Preparation of Programs for an Electronic Digital Computer'' (1951). The book offered a selection of common subroutines for handling basic operations on the EDSAC, one of the world's first stored-program computers.

When high-level languages arrived, they were introduced by numerous books and materials that explained language keywords, managing program flow, working with data, and other concepts. These languages included [[FLOW-MATIC]], COBOL, FORTRAN, [[ALGOL]], [[Pascal (programming language)|Pascal]], [[BASIC]], and C. An example of an early programming primer from these years is [[Marshal Henry Wrubel|Marshal H. Wrubel's]] ''A Primer of Programming for Digital Computers'' (1959), which included step-by-step instructions for filling out coding sheets, creating punched cards, and using the keywords in IBM's early FORTRAN system.<ref>{{cite book |last1=Halvorson |first1=Michael J. |title=Code Nation: Personal Computing and the Learn to Program Movement in America |date=2020 |publisher=ACM Books |location=New York, NY |page=80}}</ref> [[Daniel McCracken|Daniel McCracken's]] ''A Guide to FORTRAN Programming'' (1961) presented FORTRAN to a larger audience, including students and office workers.

In 1961, [[Alan Perlis]] suggested that all university freshmen at Carnegie Technical Institute take a course in computer programming.<ref>{{cite news |last=Perlis |first=Alan |title=The role of the digital computer in the university |work=Computers and Automation 10, 4 and 4B |date=1961 |pages=10–15}}</ref> His advice was published in the popular technical journal ''Computers and Automation'', which became a regular source of information for professional programmers.

Programmers soon had a range of learning texts at their disposal. ''Programmer's references'' listed keywords and functions related to a language, often in alphabetical order, as well as technical information about compilers and related systems. An early example was IBM's ''Programmers' Reference Manual: the FORTRAN Automatic Coding System for the IBM 704 EDPM'' (1956).

Over time, the genre of ''programmer's guides'' emerged, which presented the features of a language in tutorial or step by step format. Many early primers started with a program known as [[Helloworld|“Hello, World”]], which presented the shortest program a developer could create in a given system. Programmer's guides then went on to discuss core topics like declaring variables, data types, formulas, flow control, user-defined functions, manipulating data, and other topics.

Early and influential programmer's guides included [[John G. Kemeny]] and [[Thomas E. Kurtz|Thomas E. Kurtz's]] ''BASIC Programming'' (1967), Kathleen Jensen and [[Niklaus Wirth|Niklaus Wirth's]] ''The Pascal User Manual and Report'' (1971), and [[Brian W. Kernighan]] and [[Dennis Ritchie|Dennis Ritchie's]] ''The C Programming Language'' (1978). Similar books for popular audiences (but with a much lighter tone) included [[Bob Albrecht|Bob Albrecht's]] ''My Computer Loves Me When I Speak BASIC'' (1972), Al Kelley and Ira Pohl's ''A Book on C'' (1984), and [[Dan Gookin|Dan Gookin's]] ''C for Dummies'' (1994).

Beyond language-specific primers, there were numerous books and academic journals that introduced professional programming practices. Many were designed for university courses in computer science, software engineering, or related disciplines. [[Donald Knuth|Donald Knuth's]] ''[[The Art of Computer Programming]]'' (1968 and later), presented hundreds of computational algorithms and their analysis. ''The Elements of Programming Style'' (1974), by Brian W. Kernighan and [[P. J. Plauger]], concerned itself with programming ''style'', the idea that programs should be written not only to satisfy the compiler but human readers. [[Jon Bentley (computer scientist)|Jon Bentley's]] ''Programming Pearls'' (1986) offered practical advice about the art and craft of programming in professional and academic contexts. Texts specifically designed for students included Doug Cooper and Michael Clancy's ''Oh Pascal!'' (1982), [[Alfred Aho|Alfred Aho's]] ''Data Structures and Algorithms'' (1983), and Daniel Watt's ''Learning with Logo'' (1983).

===Technical publishers===
As personal computers became mass-market products, thousands of trade books and magazines sought to teach professional, hobbyist, and casual users to write computer programs. A sample of these learning resources includes ''BASIC Computer Games, Microcomputer Edition'' (1978), by [[David Ahl]]; ''Programming the Z80'' (1979), by [[Rodnay Zaks]]; ''Programmer's CP/M Handbook'' (1983), by [[Andy Johnson-Laird]]; ''C Primer Plus'' (1984), by [[Mitchell Waite]] and The Waite Group; ''The Peter Norton Programmer's Guide to the IBM PC'' (1985), by [[Peter Norton]]; ''Advanced MS-DOS'' (1986), by Ray Duncan; ''[[Learn BASIC Now]]'' (1989), by [[Michael Halvorson]] and David Rygymr; ''Programming Windows'' (1992 and later), by [[Charles Petzold]]; ''Code Complete: A Practical Handbook for Software Construction'' (1993), by [[Steve McConnell]]; and ''Tricks of the Game-Programming Gurus'' (1994), by [[Andre LaMothe|André LaMothe]].

The PC software industry spurred the creation of numerous book publishers that offered programming primers and tutorials, as well as books for advanced software developers.<ref>{{cite book |last1=Halvorson |first1=Michael J. |title=Code Nation: Personal Computing and the Learn to Program Movement in America |date=2020 |publisher=ACM Books |location=New York, NY |page=352}}</ref> These publishers included [[Addison-Wesley]], [[IDG]], [[Macmillan Inc.]], [[McGraw-Hill]], [[Microsoft Press]], [[O'Reilly Media]], [[Prentice Hall]], Sybex, Ventana Press, Waite Group Press, [[Wiley (publisher)|Wiley]], [[Wrox Press]], and [[Ziff-Davis]].

[[Computer magazine|Computer magazines]] and journals also provided learning content for professional and hobbyist programmers. A partial list of these resources includes ''[[Amiga World]]'', ''[[Byte (magazine)]]'', ''[[Communications of the ACM]]'', ''[[Computer (magazine)]]'', ''[[Compute!]]'', ''Computer Language (magazine)'', ''[[Computers and Electronics]]'', ''[[Dr. Dobb's Journal]]'', ''[[IEEE Software]]'', ''[[Macworld]]'', ''[[PC Magazine]]'', ''[[PC/Computing]]'', and ''[[UnixWorld]]''.

===Digital learning / online resources===
Between 2000 and 2010, computer book and magazine publishers declined significantly as providers of programming instruction, as programmers moved to Internet resources to expand their access to information. This shift brought forward new digital products and mechanisms to learn programming skills. During the transition, digital books from publishers transferred information that had traditionally been delivered in print to new and expanding audiences.<ref>{{cite book |last1=Halvorson |first1=Michael J. |title=Code Nation: Personal Computing and the Learn to Program Movement in America |date=2020 |publisher=ACM Books |location=New York, NY |pages=365–368}}</ref>

Important Internet resources for learning to code included blogs, wikis, videos, online databases, subscription sites, and custom websites focused on coding skills. New commercial resources included [[YouTube]] videos, Lynda.com tutorials (later [[LinkedIn Learning]]), [[Khan Academy]], [[Codecademy]], [[GitHub]], [[W3Schools]], and numerous coding bootcamps.

Most software development systems and [[game engine|game engines]] included rich online help resources, including [[integrated development environment|integrated development environments]] (IDEs), [[context-sensitive help]], [[API|APIs]], and other digital resources. Commercial [[software development kit|software development kits]] (SDKs) also provided a collection of software development tools and documentation in one installable package.

Commercial and non-profit organizations published learning websites for developers, created blogs, and established newsfeeds and social media resources about programming. Corporations like [[Apple Inc.|Apple]], [[Microsoft]], [[Oracle Corporation|Oracle]], [[Google]], and [[Amazon (company)|Amazon]] built corporate websites providing support for programmers, including resources like the [[Microsoft Developer Network]] (MSDN). Contemporary movements like Hour of Code ([[Code.org]]) show how learning to program has become associated with digital learning strategies, education agendas, and corporate philanthropy.

==Programmers==
{{Main|Programmer|Software engineer}}

Computer programmers are those who write computer software. Their jobs usually involve:
{{div col|colwidth=30em}}
*Prototyping
*Coding
*Debugging
*[[Documentation]]
*[[System integration|Integration]]
*[[Software maintenance|Maintenance]]
*Requirements analysis
*[[Software architecture]]
*Software testing
*[[Specification]]
{{div col end}}Although programming has been presented in the media as a somewhat mathematical subject, some research shows that good programmers have strong skills in natural human languages, and that learning to code is similar to learning a [[foreign language]].<ref>{{Cite journal|last1=Prat|first1=Chantel S.|last2=Madhyastha|first2=Tara M.|last3=Mottarella|first3=Malayka J.|last4=Kuo|first4=Chu-Hsuan|date=2020-03-02|title=Relating Natural Language Aptitude to Individual Differences in Learning Programming Languages|journal=Scientific Reports|language=en|volume=10|issue=1|pages=3817|doi=10.1038/s41598-020-60661-8|pmid=32123206|issn=2045-2322|pmc=7051953|bibcode=2020NatSR..10.3817P}}</ref><ref>{{Cite web |date=2020-12-15 |title=To the brain, reading computer code is not the same as reading language |url=https://news.mit.edu/2020/brain-reading-computer-code-1215 |access-date=2023-07-29 |website=MIT News {{!}} Massachusetts Institute of Technology |language=en}}</ref>

==See also==
{{Portal|Computer programming}}
{{Main|Outline of computer programming}}
*[[Code smell]]
*[[Computer network]]ing
*[[Competitive programming]]
*[[Programming best practices]]
*[[Systems programming]]

==References==
{{reflist|30em}}

=== Sources ===
* {{Cite book|url=https://archive.org/details/historyofmodernc00ceru|title=History of Computing|last=Ceruzzi|first=Paul E.|publisher=MIT Press|year=1998|isbn=9780262032551|location=Cambridge, Massachusetts|url-access=registration|via=EBSCOhost}}
*{{Cite book|url=https://books.google.com/books?id=C8ouDwAAQBAJ&q=9780735211759&pg=PP1|title=Broad Band: The Untold Story of the Women Who Made the Internet|last=Evans|first=Claire L.|publisher=Portfolio/Penguin|year=2018|isbn=9780735211759|location=New York}}
*{{Cite journal|last=Gürer|first=Denise|s2cid=6626310|date=1995|title=Pioneering Women in Computer Science|url=https://courses.cs.washington.edu/courses/csep590/06au/readings/p175-gurer.pdf |archive-url=https://ghostarchive.org/archive/20221009/https://courses.cs.washington.edu/courses/csep590/06au/readings/p175-gurer.pdf |archive-date=2022-10-09 |url-status=live|journal=Communications of the ACM|volume=38|issue=1|pages=45–54|doi=10.1145/204865.204875}}
*{{Cite journal|last=Smith|first=Erika E.|date=2013|title=Recognizing a Collective Inheritance through the History of Women in Computing|journal=CLCWeb: Comparative Literature & Culture |volume=15|issue=1|pages=1–9|doi=10.7771/1481-4374.1972 |doi-access=free}}
*Essinger, J., & EBSCO Publishing (Firm). (2014). ''Ada's algorithm: How lord byron's daughter ada lovelace launched the digital age''. Melville House.

==Further reading==
* A.K. Hartmann, ''[https://web.archive.org/web/20090211113048/http://worldscibooks.com/physics/6988.html Practical Guide to Computer Simulations]'', Singapore: [[World Scientific]] (2009)
* A. Hunt, D. Thomas, and W. Cunningham, ''The Pragmatic Programmer. From Journeyman to Master'', Amsterdam: Addison-Wesley Longman (1999)
* Brian W. Kernighan, ''The Practice of Programming'', Pearson (1999)
* [[Gerald Weinberg|Weinberg, Gerald M.]], ''The Psychology of Computer Programming'', New York: Van Nostrand Reinhold (1971)
* [[Edsger W. Dijkstra]], ''A Discipline of Programming'', Prentice-Hall (1976)
* O.-J. Dahl, [[Edsger W. Dijkstra|E.W.Dijkstra]], C.A.R. Hoare, ''Structured Programming'', Academic Press (1972)
* [[David Gries]], ''The Science of Programming'', Springer-Verlag (1981)

==External links==
{{Library resources box|onlinebooks=yes}}
{{Wikibooks|Computer Programming}}
{{Wikibooks|Windows Programming}}
{{Wikiversity|Computer Programming}}
*{{Commons category-inline|Computer programming}}
*{{Wikiquote-inline|Programming}}
<!--Please see this URL before adding external links here: http://meta.wikimedia.org/wiki/When_should_I_link_externally-->

{{Computer science}}
{{Software engineering}}
{{Software quality}}
{{Authority control}}

{{DEFAULTSORT:Computer Programming}}
[[Category:Computer programming| ]]
[[Category:Computers|Programming]]